This invention relates to hydraulic valves and systems.
The invention is more particularly concerned with proportional hydraulic valves that enable flow of hydraulic fluid in a system to be controlled and to systems including proportional hydraulic valves.
Proportional hydraulic valves have some form of actuator, so as a proportional solenoid, that moves a shuttle across an aperture so as to vary the flow of fluid through the aperture, and hence through the valve. The problem with such valves is that the flow of fluid through the valve is dependent on the pressure of fluid supplied to the valve. In order to ensure that the flow of fluid in a system is controlled independently of pressure variations, it is necessary to use an additional valve operating to maintain a constant flow rate regardless of pressure change. This leads to increased cost and complication to the system.